Semiconductor devices are produced and used throughout the world in electronic and various other types of devices. Semiconductor devices are formed on chips, and are often referred to as chips, which include millions of features and components that combine to form an integrated circuit or other semiconductor device. There is a constant push to increase integration levels of semiconductor devices by including more components on a chip of a given size, so that increased functionality can be achieved on each semiconductor device chip. As such, semiconductor device features continue to shrink and there is an ongoing drive to shrink features and components further. One aspect of feature sizes that continue to shrink is the production of high aspect ratio features on or in a substrate.
For example, the lateral dimensions of holes or trenches that extend downwardly into a substrate or into a film or films formed over a substrate, continue to shrink. Advanced processing techniques allow for these holes or trenches with shrinking lateral dimensions to be formed deeper and deeper into substrates or film or films formed above the substrates. As such, the aspect ratio continues to become greater. Practically every substrate upon which semiconductor devices are being formed, undergoes multiple wet processing operations. The wet processing operations include cleaning operations and etching operations. As the aspect ratio of holes or trenches formed on or over the substrate become greater, it becomes increasingly more difficult for the cleaning or etching fluid to extend downward to completely fill the holes or trenches. If the etching or cleaning fluid does not extend to the bottom of the holes or trenches, undesirable residue can remain after cleaning operations and undesirable material intended to be etched, can remain after etching operations. This is due, at least in part, to surface tension of the liquid that is introduced onto the surface as an etching or cleaning fluid, and can also be due to reaction products or by-products.
There is also a solid-air surface tension on the surface of the substrate that can result in voids, i.e. air bubbles, when a substrate is undergoing wet processing. This results in small areas on the substrate that are not reached by the liquid.
One technique for reducing the adverse effects due to liquid surface tension and solid-air surface tension on the surface of the substrate, is the use of a surfactant in wet cleaning. Surfactants are compounds that lower the surface tension of a liquid, the interfacial tension between two liquids, or that between a liquid and a solid. Surfactants may act as detergents, wetting agents, emulsifiers, foaming agents and dispersants. The surfactant is added to the processing liquid and is often useful in overcoming poor wettability. The surfactant assists in having the liquid coat the entire substrate surface and also in penetrating and filling high aspect ratio structures.